Cam-operated latch mechanism



3 Sheets-Sheet 1 Filed May 19, 1947 Zhwentor EDWARD S. G/FF/N (Ittornegs Nov. 7, 1950 E. s. GIFFIN CAM-OPERATED LATCH MECHANISM 3 Sheets-Sheet 2 Filed May 19, 1947 EDWARD S. G/FF/N (ittornegs Nov. 7, 1950 E. S. GIF F IN CAM-OPERATED LATCH MECHANISM Z5 Sheets-Sheet 5 Filed May 19, 1947 3nventor EDWARD 45'. GIFF'IN attorneys Patented Nov. 7, 1950 UNITED STATES PATENT OFFICE- CAM-OPERATED LATCH MECHANISM Edward Stanley Giffin, Auburn, Wash.

Application May 19, 1947, Serial No. 749,028

11 Claims.

The present invention relates to a combination lock of the type adapted to be operated by manipulation of a control member or handle in accordance with a predetermined plan, such as by moving it from a starting point back and forth through a predetermined sequence of motions terminating at a lock-release or control point. It is a primary object of the invention to provide an improved lock of this general type, characterized particularly by its positiveness of operation and its simplicity and ruggedness of construction. Because of its relatively small number of moving parts and their manner of construction, the lock may be operated an indefinite number of times without altering its combination through wear or rendering it less dependable for release each time it is properly manipulated.

A more specific object of my invention is to provide a combination lock particularly adapted for use in a self-contained switching unit for an electrical circuit, such as is described in my copending application Serial No. 572,339, filed J anuary 11, 1945, now Patent No. 2,484,991, issued October 18, 19l9, entitled Switch Mechanism. The purpose-of a lock in such a unit is to prevent unauthorized persons from tampering. with the device to operate or control the electrical circuit associated with it. The lock forming the present invention is illustratively described by reference to its application to such a switching unit because it illustrates one of the preferred uses to which the lock may be put, although the lock may readily be adapted for various other uses.

As a principal feature, my invention includes a displaceable element which can be moved from a base position to a control position to effect release or opening of the lock, such movement being produced by manipulating or moving a single actuating cam or guiding member in accordancewith the lock combination. The combination of the lock is determined by the structural formation of the cam, and more particularly by a cam track or principal guiding surface, composed of a series ofsections or ledges in switch-back arrangement which lead from a point representing the lock combination starting point, on a base or reference surface, to a combination terminal point or control point on a remote surface on the cam. Thus, the displaceable element may itself comprisea cam follower, mounted for reciprocation in the lock casing and engageable with. the cam track, or it may be operated by a cam follower, thereby to be displaced progressively in one direction as it is caused to traverse. the. track when the cam is rotated inthe manner dictated by the lock combination. The length of the different successive sections of track over which the follower travels will thereby determine the extent of the successive angular movements, respectively, making .up the lockcombination, and the number of track sections will determine the number of such movements. In the illustrated case, three ledges or track sections are employed, comprising the outer face of the. remote surface previously mentioned, and the outer surfaces of two intermediate projecting ledges extending between the hub or base surface of the cam and the ,remote surface.

Even if the displaceable element or follower is successfully started onto the track from the base surface by a person who does not know the combination, if any one of the prescribed movements of the combination is exceeded, the corresponding ledge carrying the follower will, pass beyond the follower so that it will be constrained to drop. off and return immediately, to the base surface. Conversely, by reversal of the. cam before fully carryingjout any movement of the combination; the follower williretrace its path. and fail to gain access to the next sectionlof track, eventually being returned to the base :surface.

- The follower may be constrained by suitable springineans whichwill insure that it returnto the base position whenever the look isoperated incorrectly, Furthermore, the end wallsof the ledges making, up the different sections of track, are abrupt, pitching steeply and directly down ward onto the underlying base surfacelin the'illus tratedcase, thereby giving full clearance for 're'- turn of the follower when it moves over an edge by miscalculation of the operator or at his volition in reclosing the lock after opening. 3

As an additional featureof construction, collateral guiding surfaces of track sides forming part of the cam structure, integral with the ledge formation, are provided, and these serve to direct the follower from one section of track to another, coacting with the principal surfaces or track in this respect. In addition, spring means are employed to maintain engagement of the follower with its-principal and collateral guiding surfaces and to return the follower to the base surface when the loci; is improperly operated as aforesaid. The displacement of the follower between its starting and final operating points, therefore, takes place in incremental steps, one step for each succeeding increment of the cam.

.These and other objects and features of the.

invention will now be more fully described by reference t0 the accompanying drawings, which illustrate one form of the look as it is incorporated in a switching unit of the type referred to in my said copending application.

Figure 1 is a longitudinal vertical sectional view of the switching unit, as a whole.

Figure 2 is a perspective View of the principal elements of the same unit, with parts broken away.

Figure. 3 is a front elevation view of the indicator dials for the switching mechanism and for the combination lock.

Figure 4 is a plan view, and Figure 5 is a right side elevation view of the lock with parts broken away, shown as a fragment of the switching unit of Figure 1. l

Figure 6 is a top perspective view of the cam employed in the lock, and Figure '7 is a development of the cam, made by representing circumferential lengths as linear lengths.

Figures 8A, B, and C are transverse sectional views looking rearward on line 8-8 of Figure 1, illustrating the mode of operation of the lock by showing the relative position of the lock elements at three stages during the working of the lock combination, and

Figures 9A, B, and C are transverse sectional views looking forward on line 9-9 of Figure 1, showing the corresponding positions of the latching member for the three operating stages illustrated in Figures 8A, B, and C.

Before entering into a description of the lock itself, it will be expedient first to describe generally the entire electrical switching unit in which the lock is'shown incorporated, and to point out the salient features of the construction and operation of the switching mechanism involved, for complete detail concerning which reference is made to my said copending patent application, Serial No 572,339.

The switch unit is housed within a tubular casing I!) ,overthe front end of which is fitted an indicia bearing rotary head I2, enclosing parts of y the lock; The casingis partitioned transversely bya fixed partition Mhaving holes 26 through: it, arranged in a circle. A rotor I 6, carrying elements of the switching mechanism, is received in the tube i9 rearwardly of the. partition l4, and isheld inany selected one of a plurality of possible ro-tative positions by spring-pressed ball detents [5 extending radiallyoutward. from the tube and arranged around it in spaced relation. These. detents engage cooperating notches l1 formed infthe periphery of the rotor l6. A partition l8 is lodged in tube I0 behind rotor l6, and carries contacts 33 and 35 of the switching mechanism, engaging contact segments 3| on the back of the rotor. A frontpartition forms part of the structure of the lock. All of the partitions l4, l8 and 29 have threaded peripheries and screw int'oa thread on the inside of the casing ID,

The switching mechanism is controlled primarily. by a longitudinal rod 22 extending axially of thecasing through bores in the several parti tions and the rotor I6. The rotary head i2 is carried by the outer end of the rod and is rotatable with it. The rod 22 is guided for rotation and for reciprocation axially of the unit by such bores; the former movement being employed in positioning,a switch control member in the form of an arm 23 projecting radially from such rod and carrying a head 24which may be brought into registry with any one of the several circumferentially arranged apertures 26 in the partition 14. By the second typeof manipulation the head may be reciprocated rearwardly and passed through the registering aperture to engage a cooperating contact element 28 of the switch mechanism mounted resiliently on rotor 16 by a spring leaf arm 28 connected to one of the contact segments 3|. By projection of head 24 through the aperture 26 behind which is located the contact 28, such contact will be pressed inwardly into engagement with its cooperating contact 29 mounted yieldably for axial, overtravel movement in rotor I6, and connected to the other contact segment. By such contact engagement the arcuate plates 31, and hence the switch terminals 33 and 35 contacting these plates, will be connected, to energize the electric circuit in which the switching mechanism is connected.

However, as will appear from my copending application mentioned above, if the actuating head 24 is pushed through an aperture 26 other than that in registry with contact 28, as by an unauthorized person attempting to operate the device, the switching mechanism will not be actuated when the rod 22 is thrust inwardly. Moreover, it will then become locked by the mechanism described below, to prevent further tampering. If the unitis used to control the ignition circuit of an automobile, it can be incorporated as another feature in the dashboard of the vehicle, where the switch indicia dial S and pointer P may be readily visible to the operator. Each number 29, 30, 31, etc. on the dial corresponds to a different aperture 26 of the partition.

AS explained in greater detail in my copending application, the switch contact member 28 may be shifted at thewill of the operator into registry with any aperture 26 of the partition M, thus 'to establish any of the numbers on the dial S as the switch-closing number, with the exception of that corresponding to the slot 21 in partition l4. Such shifting of the contactmember 28 is effected by turning the pointer P until it registers with the number on dial S corresponding to such slot, and

then pressingjrod 22 inwardly to move the actuating head 24 and its supporting arm 23 completely through the slot. To complete such in- Ward movement it may benecessary to release the locking mechanism described hereinafter.

After thus being moved axially inward rod 22 isrotated in one direction or the other to bring the actuating head 24 into engagement with one ping from one groove l'1 into an adjacent groove,

so that the rotor will always be brought to rest in a position to locate the contact element 28 in registry with an aperture 26 of partition I4. When the contact has thus been aligned with the desired aperture the rod 24 is rotated in the reverse direction, again to dispose its arm 23 in registry with slot 21, so that by drawing rod 22 outwardly the arm and head again may be disposed at the side of partition l4 opposite that adjacent to contact member 28.

The lock dial L is carried by the margin of the rotary head l2, so that it is rotated with such head. Any one of the numbers of dial S, such as 10,- may serve as an index for this lock dial.

The device is shown in its switch-open position in Figure 1. In that position spring-pressed ball detents 32 mounted in a partition 33 are engaged in an annular groove 31 formed in rod 22,

grooves 30 and 37 determining the extent of 1 movement of rod 22 between such positions.

Whenever rod 22 is moved inward so that groove 30 passes beyond detents 32, whether actuating head 24 has been disposed in registry with an aperture other than that in registry with contact element 28 or in registry with slot 21, my locking mechanism, if conditioned for operation, will act to lock the rod against outward movement until the lock. has been released. To render such locking action effective, precautions should be taken in the design of the mechanism to prevent detents 32 engaging too securely in groove 30. Thus the springs of these detents should be very light, or groove 30 should be quite shallow, or both, toprevent an unauthorized operator detecting engagement of such detents in that groove, while at the same time the detents Will afford sufficient holding engagement with the groove to prevent inadvertent lengthwise shifting of the rod.

If the correct aperture for engaging actuating head 24 with contact element 28 is not known to the operator, and the rod 22 is reciprocated to move such head into some other aperture, its

inward movement will not be limited by engagegroove 30 well beyond the detents 32, and to the point where an abrupt annular groove 34 in the rod is brought into registry with a latch plate 36. Normally this latch plate rests slidably on the rod, but it is urged against the rod by spring pressure, so that upon registry of notch 34 with it, it drops into the notch and prevents outward withdrawal of the rod for another operation trial by the unauthorized operator.

Therefore, only an authorized person having the information necessary to operate the switching mechanism, by knowing the relative positional relationship of the actuating element 28 and of the apertured partition [4, as indicated by the numbers on dial S, can hope reasonably to close the switch. This relationship, which may be changed by the owner in the manner described above, may easily be altered from time to time as a means of obtaining security against unauthorized operation. Once the'mechanism has been locked by improper manipulation it cannot again be operated unless the combination of the lock is known to the operator so that it can be opened, lifting the latch 36 from the notch 34, whereupon the rod 22 may be withdrawn by the operator.

The lock, of which the latch 36 forms a part, will now be described, along with the manner in which it operates to raise the latch out of the notch 34 to allow withdrawal of the rod 22. The lock includes, as its principal elements, a rotary cam element designated generally as C, and. a cam follower designated generally as F, engageable with the cam. The cam follower includes a;swingable arcuate arm 40, preferably semi- ,circular,,,one end of which is pivotally and slidably mounted: on a fixed pin 42 projecting from the front face of partition 20. The opposite end of the pin may extend through the partition and serve as a pivotal support for the latch plate 36. Thus the latch and arm are disposed on opposite sides of the partition. Interconnecting the latch and cam follower arm for conjoint movement is a coupling pin 44 carried by the latch plate, which pin passes through an arcuate slot 46 in the partition 20, swinging the latch about the axis of the supporting pin 42 as the cam follower is displaced by the cam.

To support the latch against tilting or axial displacement, thus preventing breakage, in case the lock is forced, I have provided a headed stud 4B threaded in or otherwise anchored to the partition 20, which holds the latch against an inward thrust of the rod 22 when the latch is engaged in the notch 34. Further, to allow the latch to be swung about its supporting pin 42, the stud 48 extends through an arcuate slot 50 formed in the latch plate. The latch itself is preferably of crescent shape, its concave edge being notched or recessed to embrace closel the reduced portion of rod 22 at the bottom of notch 34', so that with the latch engaged in the notch 3 there is a line of contact around a large fraction of the periphery of the rod to form a contact zone of substantial area. The inner end of a reversely bent or U-shaped pin 52 acts as the cam contacting member of the cam follower. The outer end of the pin away from the cam is secured to the follower arm MI at a point approximately midway between its ends. The cam follower is acted upon by two forces, to urge pin 52 always rearwardly and radially inwardl into contact with the cam, produced conveniently by' two spring members 54 and 56, respectively. The first spring encircles the end of the supporting pin 42 projecting forward from partition 20. and is compressed between the head of such pin and the outside of the arm 40 to urge the arm rearwardly toward the partition. The second spring 55 is a tension spring having one end connected to the swinging end of arm 40' and its other end to an anchor pin 58 secured in and projecting from the front side of the partition 20, tending to swing arm 40 inwardly.

In order to raise and lower the cam follower to operate the latch correspondingly, the cam is rotated Or oscillated about the central axis of the unit in a predetermined manner, in accordance with the lock combination. This is accomplished by turning a control knob 59 integral with and forming a central projection of the the rotar head l2. Preferably the body of the cam is a separate element fitted over a shouldered sleeve 64 which is received loosely on rod 22' and has a flange 65 bolted to the inner face of the end of the rotary head l2. 'The cam element is secured to sleeve 64 by a readily removable pin or screw 62 so it can easily be removed from the sleeve 50- that a cam element having a cam track of different shape may easily be substituted for that, shown. The inner end of sleeve 64 projects through a central aperture of partition 20 and is threaded to receive retaining nuts 66 which abut the rearward side of the partition to secure the cam and rotor sleeve assembly in the unit.

The projecting end of rod 22 which carries the knob 61 is of noncircular shape, being represented as square, although it .may be splined, keyed, or of any other noncircular shape in cross section. A sleeve 68 fitted over this end of the rod 22. has abore shaped complementally, so that mation projects, is labelled 14.

while the rod'may. be reciprocated lengthwise through this sleeve, rotation of-the rod will turn .such sleeve. This sleeve is held againstendwise movement by being shouldered to engage with a complemental annular shoulder within the knob 60. The inner end of sleeve 68 abuts the forward face of flange 65 formed on the end of sleeve 64. Consequently sleeve 68 cannot be moved, endwise with respect to the rotary head [2, although it may be turned relative to it by rotation of rod 22.

Sleeve 68 carries the pointer P, which i secured to it by the nut 69 threaded on the end of such sleeve. As rod 22 is turned, therefore, the pointer P will be turned in synchronism with it, to register with the various numbers on the dial S corresponding to the several holes 26 in partition 14, as explained previously. Conversely, rotation of the knob 68, and hence of the cam C, may be effected independently of the angular position of the rod 22 and of the pointer P. r

The flange H of head l2 bears the dial L hav ing the lock combination numbers arranged circumferentially around its outer edge, so that as the cam is rotated relative to the cam follower in working the lock combination, its exact position will be made known to the operator by the relationship of the dial numbers to the indicator number of dial S. The numbers or critical points of the lock combination may readily be altered or shifted through an angle relative to the casing by repositioning the cam C rotationally on the sleeve 64, such as by inserting pin 62 in any one of a series of holes arranged circumferentially around the sleeve, or by securing the flange 65 of sleeve 64 in different circumferentially adjusted positions relative to rotary head I2 by the arrangement of the threaded holes for the screws 10 holding together the rotary head 12 and the flanged sleeve 64 and alternatively engageable for the purpose.

Generally, in the construction of the particular cam illustrated, there is a base or reference surface on which the cam follower, when groove 34 is in registry with latch plate 36, rests withthe lock closed. Continuing from this, surface and leading therefrom to a remote surface, is a discontinuous or switchback track oVer which the follower will be displaced; by oscillation of the cam in accordance with the combination, in moving between the surfaces to raise the latch'and open the lock. In order that the cam follower, being in fixed angular position, may traverse the length of the cam track of switch-back conformation, it is necessary to reverse the direction of rotation of the cam each time an intersection between connected track sections reaches the follower. The lengths of the track sections thereby surface of which acts as the base or reference surface of the cam. The cam track leads generally outwardly from the hub up the side of the cam sleeve flange 63 as a ledge formation projecting outwardly from the face of such flange, as shown best in Figures 6 and 7. The side or face of the cam element flange carried by the hub 12, from which the switchback cam ledge for- The switchback track over which the cam follower travels defines a path comprising a series or flight of track sections 16', 16", of generally spiral arcuate shape,

;which ascend gradually from the base surface '12 8 to the remote track section surface 18. The surface 78 is nominally designated by the term fremote to impart the idea of displacement, since when the cam follower is moved up or over the track it becomes displaced radially by an amount sufficient to raise the latch 36 out of its notch 34 when the follower reaches the end of this surface. In the illustrated case, two intermediate sections of track have been employed; in addition to the remote track section 18, thereby requiring a lock combination manipulated by three oscillatory movements of the cam.

If the cam is rotated continuously in a clock.- Wise direction, the follower 52 can not ascend even the first track section 16 but will simply traverse the periphery of the base surf-ace or hub of the cam. During such movement the follower will be. pressed against the forward surface 14 of the flange 63 by spring 54, being shifted outwardly therefrom by engagement with it of the collateral guiding surface 80, forming the side of the ledge beneath the first section of track 16'. For this reason, the collateral or side surface 80 is curved and faired smoothly into the face of the surface 14 at the end which first encounters the follower, to offer the minimum resistance to continuous clockwise rotation of the cam. As rotation of the cam clockwise is continued, the height of the collateral guiding surface 80 diminishes to the point where the track 76 becomes substantially tangential to or flush with the base surface, at which point the follower pin slips over the surface 16' and is thrust rearwardly by the spring 54 into contact with the surface '14 beneath the overhanging ledge f-orming the seotionvof track 16". This point of rotation may constitute the starting point of the combination.

In order to bring the first section of track 16' into engagement with the cam follower the cam must be rotated counterclockwise by turning knob 66, and the continued movement of the track beneath the follower will press it outwardly against the resilience of spring 56 acting on arm 40, because of the spiral conformation of the track section. As the track thus moves beneath the follower the vertical collateral guiding sur-v face beneath the track section 16" will wedge the follower forwardly against the resilience of spring 54 acting on arm 40, until it reaches the junction between track sections 16' and 16".

To release the lock successfully the cam must not be rotated so far in the counterclockwise direction that the follower will drop off the junction of the track sections 76 and 16", shown in Figure 6, to be returned to the base surface 12 by the force of spring 56 acting on follower arm 40. If, after the junction of the track sections 16 and 16" has been'engaged with the follower, so that it will be shifted rearwardly again by spring 54 'into engagement with the flange surface 14, ro-

tation of the cam is reversed, the track section 16" will be moved beneath the cam follower to urge it still farther away from the base surface 12 in opposition to the force of spring 58.

As the cam track section 16" continues to move beneath the follower pin 52 during such rotation of the cam, again it will be wedged forwardly, as well as outwardly, by engagement with it of a vertical collateral guiding surface beneath the remote track section 18 and inclined away from surface 14, until the junction between track sections 16 and 18 is engaged with the cam follower. At this point the-spring 54 again will shift the arm 40and follower 52 rearwardly, until the follower once more engages the surface 14.

If rotation of the cam is continued in the clockwise direction too far by one unfamiliar with the combination, the follower will drop from the intersection of track sections 16 and 16'', to be returned to the base surface 12 by spring 56 acting on arm 40, just as would occur by excessive rotation of the cam when the follower is engaged with the junction of track sections 16' and 16'. If the cam rotation is reversed from clockwise to counterclockwise in time, however, the remote track section 18 will be moved beneath the cam follower, to shift it still further outward, so that when it approaches the outer end of this track section the lock will be released.

As has been mentioned previously, the cam follower 52 is carried by the arm 40 pivoted on the pin 42, and this arm in turn is connected to the latch plate 36 by the interconnecting pin 44. The progressive outward displacement of follower 52, arm 40, and latch plate 36, as the several cam track sections are moved beneath the cam follower in the manner described, is illustrated in Figures 8A to SC and 9A to 90 inclusive. Thus in Figure 8A the cam follower 52 is engaged with the base surface 12 of the cam C, at which time the latch plate 36-is engaged in latched position in the groove 34 of rod 22. As the cam follower is moved outward by oscillation of the cam until the junction between track sections 16 and 18 contacts the cam follower, the latter is moved progressively into the position of Figure 8B. By such movement the arm 40, and the latch plate 36 connected with it, are swung outward about the axis of pin 42 into the respective positions shown in Figures 813 and 93. It will be noted that such swinging has not completely released the latch plate 35 fro-m the shoulders of the rod groove 34, because of the considerable depth of the rod-engaging notch in that plate made possible by its crescent shape.

Actually when the junction of cam track 16" and i8 is engaged with cam follower 52, as shown in Figure 8B, the latch plate 36 has been swung outwardly only about half as far as necessary for it to clear the rod notch 34. In order to free the latch bar completely from the notch, therefore, the remote track section 78 is of a length approximately equal to the combined lengths of track sections 16. and 16'. Consequently movement of the track section 18 beneath the cam follower will wedge it outwardly from the position of Figure 83 to that of Figure 80, so that the bar 40 and latch plate 33 will be swung outward sufficiently far, as shown in Figures 8C and 90, respectively, to raise the latch plate completely out of the rod notch 34.

If the switch actuating head 24 has been pushed into an aperture 26 other than the one in registry with contact element 28, therefore, or if it has been moved in one direction or the other part way through slot 21 in partition I4, the latch plate in that released position will not interfere with movement of the rod either inward or outward from the position in which its groove 34 is in registry with latch plate 36. After such movement, even though the knob 66 is rotated so that the cam track passes out of engagement, with the cam follower, and it is returned toward the base section, inward movement of the latch plate will be interrupted by the edges of its notch striking the outer surface of the rod so that the latch plate will merely ride along the rod as it is reciprocated, until once again the notch 34 has been brought intoregistry with the latch plate. At that time spring 56 will iii 10 swing arm 40 and the latch plate inward into latched position without any rotation of the cam element C being required.

It is not necessary to employ the particular cam track formation herein shown, in. which each outer section is positioned directly over the inner section or sections; however, to do so makes it possible conveniently to limit the expansion and contraction necessary in the operation of the spring 54 to an amount equal to the greatest projection of the cam track beyond surface 14.

It has been stated that the entrance to the track section 76 may be defined by the point at which the cam follower pin clears the side 80 of the first ledge and moves rearwardly onto the track as the cam is turned clockwise, which point may correspond to the first number of the lock combination. It will be apparent, however, that this number is not critical, inasmuch as any number of several may be selected as a starting point if the cam is first rotated counterclockwise from that point to the number corresponding to the location of the first switch,- back point in the track at the junction of track sections 16' and 16".

Thus, in Figure 8A, assuming the numeral 40 of the fixed dial S to be the index point for the lock combination dial L, the starting point of the combination may be any number from 1 to 18, the latter number being aligned radially with the beginning of the track section 16 as indicated by the line 1 of Figure 8A. In order to bring the first track section 16 under the follower pin 52 up to the first switchback point, which pin is shown positioned in line radially with the numeral 40, the cam may be rotated counterclockwise to the number 22 which is aligned with this point radially, along line a: of Figure 8A. I

Thereafter, the combination is determined by the length of the track sections 16 and 18, the dial L being next rotated clockwise from number 22 to the number 16, at which the follower shifts onto the remote track surface 18,

and finally counterclockwise to number 23, corresponding to the outer end of the remote surface. At this point the cam follower is elevated to its extreme position, and with it the latch 36, which is then released from the notch 34.

The combination may be made very critical by reducing the length of the track section junctions to approximately the width of the pin 52. The angular movement of the dial L during the elevation of the cam follower by the cam may be taken into account by adding to or subtracting from the length of the track sections in their design, in order that the switch-back points may be made to register exactly with selected numbers or marks of the combination dial.

In order to return the cam follower to the base surface, when the pin 52 is perched. at the end of the remote surface 18, the cam may be rotated counterclockwise a slight distance further to drop the pin over the edge, or it may be rotated clockwise the length of the remote surface and beyond, to the same end. It is not possible to return the follower otherwise because of the action of the spring 54 in forcing the follower rearwardly against the side of the cam, because of which it cannot drop directly to the adjoining track section 16".

It will now be apparent that the same results may be achieved by cams and cam followers of different forms. For example, instead of sin-- 11 ploying a direct connection'between the follower 52 and the latch 36 to cause the latch to move always conjointly with the follower as the latter is displaced by the cam, a lost-motion type of connection-may be employed, whereby, during the initial lifting of the follower by the cam track, there will be no effect on the" latch. In this case, the latch could be tripped during the last increment of outward displacement of the cam follower by the action of suitable means interengaged between the latch and the follower.

Furthermore, an alternative form ofcam may be employed whereby the cam follower becomes displaced, not radially, but in a direction generally parallel to the axis of rotation of the cam. Accordingly, the collateral or side guiding surfaces of the present track sections can be modified appropriately to act as the principal guid-. ing surfaces. which, in a practical application, will define a track progressing in successively reversed stages lengthwise of the cam, instead of radially of the cam., The manner of designing a cam-capable of operating in this way may be based on the same principles, namely, to provide a trackwith suitably located switchba-ck points which are bordered by follower-return points so that incorrect manipulation of the lock will return the follower to a base surface or point.

I claim as my invention:

1. A lock comprising a tubular casing, a rotatable and reciprocable rod lockable against reciprocation and supported and guided in said casing for rotation and reciprocation axially thereof, handle means to reciprocate and rotate said rod in said casing, a latch carried insaid casing and-mounted for reciprocation toward and away from said rod, latch-engaging means on said rod movable with said rod axially of said casing into latch-engageable position, cam-means rotatably mounted in said casing and having a bore through which extends said rod in slidable relation thereto, means for rotating said cam means, and cam-follower means coacting with said cam means, mounted in saidcasing for radial movement, and operable to effect movement of said latch by'predetermined rotational movement of said carnmeans.

2. A look comprising a tubular casing, tatable and reciproca-ble rod lockable against reciprocation and supported and guided in said casing for rotation and reciprocation axially thereof, handle means to reciprocate and rotate said rod in said casing, a latch carried in said casing and mounted for reciprocation toward and away from said rod, latch-engaging means on said rod movable with said rodaxially of said casing into latch-engageable position, cam means rotatably mounted in said casing and having a bore through which extends said rod in slidable relation thereto, means for rotating said cam means, and cam-follower means coacting with said cam means, mounted in said casing for axial. and radial movement, and operable to effect movement of said latch by predetermined reversed angular rotational movements of said cam means, said cam'means having a switchback track engageable by said cam follower and which progresses from a peripheral base surface to a remote surface.

3. A look as defined in claim 2, in which the cam-follower means comprises spring means operable to return the cam-follower means tothe base surface each time the limits of the track are exceeded by angular movement of the cam means,.

' 4. Locking mechanism comprising latch-secured means, a latching element mounted for movement reciprocably relative to-said' latchsecured means, and cam mechanism operable to effect movement of said latching element out of; securing position including a cam member, a cam follower engageable with said cam member and operatively connected to said latching ele-' ment to effect its releasing movement by movement of said cam'member, a cam supporting member, and means normally interconnecting said cam supporting member and said cam-member, readily removable for replacement ofsaid cam member'by another cam member.

5. Locking mechanism comprising latch-secured means, a latching element mounted for movement reciprocably relative to said latchsecured means, and cam mechanism operable to effect movement of said latching element out of securing position including a cam member, a cam follower engageable with said cam member and operatively connected to said'latching element to effect its releasing movement by move-3 ment of'said cam member, and a recessed head receiving said cam member and cam follower in the recess thereof, and securedto said cam member for rotation therewith, said recessed head carrying an indicator dial bearing marks adapted to indicate lock operating positions of said cam member. 7

6. Locking mechanism as defined in claim 5, and connecting means interconnecting the re-. cessed head and cam member in a selected one of a plurality of selectable relatively rotated positions. V

7. In locking mechanism of the cam operated type, including a rotatable cam member incorporating a cam track, the combination comprising a notched rod, a latch plate, a cam follower coacting with the cam track and operatively connected to said latch plate, and means jointly supporting said cam-follower and said latch plate for conjoint swinging movement relative to said notched rod, to effect engagement and disengagement of said latch plate with the notch in said rod when said cam follower is displaced by predetermined rotational movement of the cam member. 1 t

' 8.'Locking mechanism as defined in claim7, in which the latch plate is generally of crescent shape with a deep notch in its concave side approximately mid-way between its ends which is engageable with the notched portion of the rod.

9. A lock as 'defined'in claim 2, in which the switch-back track comprises arcuate peripheral sections inclined successively reversely of a circular line drawn about the axis of the shaft as center, and additionally comprises collateral surfaces respectively adjacent said sections on one side of the cam block, and means operable to effect engagement of the cam-follower means and the cam means including spring means urging the cam-follower means radially into contact with said peripheral sections of track and axially of the cam against said collateral surfaces, successively, upon predetermined rotational movements imparted to the cam.

10. Looking mechanism adapted to perform a controlfunction, comprising a rotatable, lengthwise reciprocable rod having a groove therein, a

latch plate, meanssupporting said latchplate for swinging about a'naxis generally parallel to said rod, between a locked position engaged insaid groove and an unlocked position withdrawn from h oov and ro atable loci; mechanism in- 13 eluding a cam concentric with said rod, and cam follower means operatively connected to said latch plate and. operable by rotation of said cam to swing such latch plate about its pivot from its locked position in said groove to its unlocked position withdrawn from such groove thereby to release said rod for lengthwise reciprocation to perform a control function.

11. The locking mechanism defined in claim 10, wherein the cam follower means comprises a cam follower element operatively engageable with said cam, and supporting means for said cam follower element, rotatable about the axis of swing of the latch plate by operative movement of said cam follower element, and means operatively inter- 15 EDWARD STANLEY GIFFIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 565,527 Weber Aug. 11, 1896 836,976 Johnson Nov. 27, 1906 

